Record symptoms
Note which emitters are affected, when the problem occurs and whether controls, valves or balancing change it.
System-water evidence
How can I tell if my heating system has sludge?
Dark water, cold areas, noise or restricted circulation may be consistent with debris or corrosion products, but symptoms cannot confirm the location, quantity, cause or required treatment.
Build a clearer picture
Check sampled water
Consider turbidity, inhibitor and pH information together and recognise that one sample cannot represent every part of a system.
Investigate professionally
A competent professional can inspect circulation, components and system condition before recommending work.
Do not diagnose from one sign
Similar symptoms can result from valves, balancing, pumps, controls, trapped air or component faults. Evidence should guide investigation, not trigger automatic cleaning.